[bobthepanda]

Haijin wasn't really meant to stop people from becoming more powerful than the court. It was supposed to starve out Japanese pirates.

In reality, the people who were trading mostly continued to do so, becoming pirates and smugglers themselves in the process, and Ming China simultaneously lost a bunch of tax revenue from trade as well as tying up a huge part of the labor force in enforcing a sea ban.

The Qing policy was more successful but also required all property destroyed within 30 miles of the coast or face the death penalty, which is extreme to say the least.